A dwarf with a disk

Ron Cowen

The Hubble Space Telescope has examined in unprecedented detail a ring of debris around a star that could be the nearest and youngest known home for planets outside the solar system. Researchers described the findings during a NASA briefing last month.

The disk surrounding the young star, called AU Microscopii, is the product of collisions between unseen planets and the debris left over from their formation, researchers say. A central hole in the disk, found by Hubble and other telescopes, may have been cleared by a massive planet.

Residing just 32 light-years from Earth, AU Microscopii is the first red dwarf star found to have a debris disk. "Understanding the evolution of [red dwarf] disks may tell us about how the majority of planetary systems evolve," comments Paul Kalas of the University of California, Berkeley. Red dwarfs are among the most common stars in the Milky Way. Kalas' team reported the disk's discovery early last year.

Using Hubble's Advanced Camera for Surveys, a team led by John Krist of NASA's Jet Propulsion Laboratory in Pasadena, Calif., found a warp in the disk at a distance from the star of about 50 times the Earth-sun distance. The warp could be from the tug of an outlying planet.

The warp and other traits of AU Microscopii's disk resemble those of the disk surrounding a much more massive star, Beta Pictoris, in the same star cluster. The similarity suggests that the disk surrounding Beta Pictoris, first observed 20 years ago, isn't a freak of nature but is typical of young debris disks, says Michael Liu of the University of Hawaii in Honolulu.

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References:

2004. Spitzer and Hubble capture evolving planetary systems. California Institute of Technology/Jet Propulsion Laboratory press release. Dec. 9. Available at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/33/.

Krist, J.E., et al. In press. HST/ACS coronagraphic imaging of the AU Microscopii debris disk. Astronomical Journal. Preprint available at http://lanl.arxiv.org/abs/astro-ph/0410466.

Sources:

Paul Kalas
Astronomy Department
Radio Astronomy Laboratory
601 Campbell Hall
Berkeley, CA 94720

John E. Krist
Space Telescope Science Institute
3700 San Martin Drive
Baltimore, MD 21218

Michael C. Liu
Institute for Astronomy
University of Hawaii, Honolulu
2680 Woodlawn Drive
Honolulu, HI 96822

From Science News, Volume 167, No. 2, January 8, 2005, p. 30.